[PPT] - Design of a Lightweight, Portable Hydraulic Power Supply Jonathan PowerPoint Presentation

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Fluid Power Innovation & Research Conference Minneapolis, MN | October 10 - 12, 2016

Design of a Lightweight, Portable Hydraulic Power Supply

Jonathan Nath, M.S. Student William Durfee, PhD University of Minnesota

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Project Objectives

Develop an analytical model to aid in the

system level design of a minimal-weight portable hydraulic power supply

Develop design guidelines for optimal

component integration techniques

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Motivation

October 2015 CCEFP Strategic Research Plan (SRP)

identifies excessive weight and size as a barrier for new portable applications, and particularly for new human-scale applications

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http://www.jawsoflife.com/en/product/edraulic-s700e2-cutter

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Methods for Minimizing Weight

Optimal Component Selection Using Computer

Modeling

– Battery, motor, pump parameter selection

Component Integration

– Packaging techniques – 3D Printing

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https://www.asme.org/engineering-topics/articles/manufacturing-processing/spotlight-tim-simpson-penn-state-cimp3d

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3D Printing

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http://3dprint.com/89974/googles-atlas-3d-print-robot/

Boston Dynamic: Atlas Child Hydraulic Ankle-Foot Orthosis: 3D Printed Titanium Version

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Hydraulic Ankle-Foot Orthosis

Brushless DC Motor Untethered, hydraulic power supply Axial piston pump Lithium polymer battery Gearbox Hydraulic actuators

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Power Supply Configuration

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http://www.maxonmotorusa.com/

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Circuit Selection

Throttling valve configuration Electro-hydraulic actuator (EHA)

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Motor and Pump Selection Procedure

Basic Procedure

Pressure Flowrate Pump Electric Motor

Optimized Procedure

Does not consider operation efficiency

Pressure Flowrate Run Time Pump Electric Motor Battery Size Swashplate Angle Size

Considers operation efficiency

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Motor Modeling

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No-load Losses

Core losses (magnetic losses/iron losses): alternating magnetic flux produces hysteresis losses and eddy current losses in

the stator and rotor cores, magnets, and other motor components

Mechanical losses: including bearing friction

Load Losses

Resistive losses (copper losses): losses in the windings

𝑄

𝑑 = 𝐽2𝑆

Mechanical Design of Electric Motors: Wei Tong

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Motor Modeling: Maximum Power 𝜃 = 𝑄𝑝𝑣𝑢 𝑄𝑗𝑜 At Steady-State: 𝑄𝑗𝑜 = 𝑄𝑝𝑣𝑢 + 𝑅𝑝𝑣𝑢 𝑅𝑝𝑣𝑢 = 𝑄𝑗𝑜 (1 − 𝜃)

𝑈

𝑥𝑗𝑜𝑒𝑗𝑜𝑕 = [𝑄𝑗𝑜 ∗

1 − 𝜃 ∗ 𝑆𝑢𝑝𝑢𝑏𝑚] + 𝑈

𝑡𝑣𝑠𝑠𝑝𝑣𝑜𝑒𝑗𝑜𝑕

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Motor Model: Validation

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http://www.maxonmotorusa.com/

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Battery + Motor Configuration Case Study

0.140 kg R = 0.608 Ohm Kt = 0.036 Nm/A 0.390 kg R = 1.01 Ohm Kt = 0.091 Nm/A

70W 100W

3600 run time
Picked 4 steady-state operating points
Calculated overall system weight, battery + motor

vs.

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http://www.maxonmotorusa.com/

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Motor Case Study: Results

0.5 Nm, 100 rad/sec 0.39 Nm, 150 rad/sec 0.28 Nm, 200 rad/sec 0.05 Nm, 300 rad/sec

Increasing torque 14

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Large vs. Small Motor

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Copper Losses: 𝑄

𝑑 = 𝐽2𝑆

Resistivity: 𝑆 =

𝜍𝑀 𝐵

If L is doubled, Pc is cut in half

http://www.maxonmotorusa.com/

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Axial-Piston Pump Modeling

Required torque w/o friction Viscous friction loss, pistons and cylinder block Coulomb friction, pistons and cylinder block Viscous friction, slippers and swash plate Viscous friction, valve plate and cylinder block

Jeong, H., 2007. “A novel performance model given by the physical dimensions of hydraulic axial piston motors: model derivation”. Journal of Mechanical Science and Technology, 21(1), pp. 83–97.

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Axial-Piston Pump Modeling

Jeong, H., 2007. “A novel performance model given by the physical dimensions of hydraulic axial piston motors: model derivation”. Journal of Mechanical Science and Technology, 21(1), pp. 83–97.

Flowrate w/o leakage Leakage between pistons and cylinder block Leakage between valve plate and cylinder block

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Axial-Piston Pump Model: Validation

Model compared to Takako miniature axial-piston pump line performance

0.4 cc/rev Pump Comparison, 200 rad/sec 18

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Combined System Model

Inputs

Desired Run Time Desired Flowrate Desired Output Pressure

Iterative Component Variables

Motor Sizing Pump Sizing Swashplate Angle

Output

Motor size, pump size, swashplate angle to achieve minimum system weight

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Fixed Pump, Variable Motor Size

>155 W required, 245 W for minimum system weight >155 W required, 155 W for minimum system weight 20

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Fixed Motor Size, Variable Pump Parameters

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FPIRC16 0.5 hour run time, 10 Mpa, 10 cc/sec 124W Motor, 1.24 kg 193W Motor, 1.16 kg 285W Motor, 1.48 kg 95W Motor, 0.84 kg 22

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FPIRC16 124W Motor, 7.97 kg 193W Motor, 7.23 kg 285W Motor, 8.11 kg 95W Motor, 8.04 kg 8 hour run time, 10 Mpa, 10 cc/sec 23

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Uses for the Program

Can be used to provide an exact custom

solution for a minimum-weight power supply

Could be used to help guide selection of off-

the-shelf components

– Fix pump and select optimal motor size – Fix motor to select optimal pump size

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Next Steps

Expand from steady-state to a quasi-static

analysis

Eventually consider dynamic operation
Create test stand to validate system modeling

and explore optimized integration techniques

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Conclusions

Required system pressure, flowrate, and

runtime are what drive an optimized design

A system that is optimized for one set of

desired outputs will likely not be a minimum- weight solution for another set of outputs

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Questions?

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